// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2008-2014 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_COREITERATORS_H
#define EIGEN_COREITERATORS_H

namespace Eigen {

/* This file contains the respective InnerIterator definition of the expressions defined in Eigen/Core
 */

namespace internal {

    template <typename XprType, typename EvaluatorKind> class inner_iterator_selector;

}

/** \class InnerIterator
  * \brief An InnerIterator allows to loop over the element of any matrix expression.
  * 
  * \warning To be used with care because an evaluator is constructed every time an InnerIterator iterator is constructed.
  * 
  * TODO: add a usage example
  */
template <typename XprType> class InnerIterator
{
protected:
    typedef internal::inner_iterator_selector<XprType, typename internal::evaluator_traits<XprType>::Kind> IteratorType;
    typedef internal::evaluator<XprType> EvaluatorType;
    typedef typename internal::traits<XprType>::Scalar Scalar;

public:
    /** Construct an iterator over the \a outerId -th row or column of \a xpr */
    InnerIterator(const XprType& xpr, const Index& outerId) : m_eval(xpr), m_iter(m_eval, outerId, xpr.innerSize()) {}

    /// \returns the value of the current coefficient.
    EIGEN_STRONG_INLINE Scalar value() const { return m_iter.value(); }
    /** Increment the iterator \c *this to the next non-zero coefficient.
    * Explicit zeros are not skipped over. To skip explicit zeros, see class SparseView
    */
    EIGEN_STRONG_INLINE InnerIterator& operator++()
    {
        m_iter.operator++();
        return *this;
    }
    EIGEN_STRONG_INLINE InnerIterator& operator+=(Index i)
    {
        m_iter.operator+=(i);
        return *this;
    }
    EIGEN_STRONG_INLINE InnerIterator operator+(Index i)
    {
        InnerIterator result(*this);
        result += i;
        return result;
    }

    /// \returns the column or row index of the current coefficient.
    EIGEN_STRONG_INLINE Index index() const { return m_iter.index(); }
    /// \returns the row index of the current coefficient.
    EIGEN_STRONG_INLINE Index row() const { return m_iter.row(); }
    /// \returns the column index of the current coefficient.
    EIGEN_STRONG_INLINE Index col() const { return m_iter.col(); }
    /// \returns \c true if the iterator \c *this still references a valid coefficient.
    EIGEN_STRONG_INLINE operator bool() const { return m_iter; }

protected:
    EvaluatorType m_eval;
    IteratorType m_iter;

private:
    // If you get here, then you're not using the right InnerIterator type, e.g.:
    //   SparseMatrix<double,RowMajor> A;
    //   SparseMatrix<double>::InnerIterator it(A,0);
    template <typename T> InnerIterator(const EigenBase<T>&, Index outer);
};

namespace internal {

    // Generic inner iterator implementation for dense objects
    template <typename XprType> class inner_iterator_selector<XprType, IndexBased>
    {
    protected:
        typedef evaluator<XprType> EvaluatorType;
        typedef typename traits<XprType>::Scalar Scalar;
        enum
        {
            IsRowMajor = (XprType::Flags & RowMajorBit) == RowMajorBit
        };

    public:
        EIGEN_STRONG_INLINE inner_iterator_selector(const EvaluatorType& eval, const Index& outerId, const Index& innerSize)
            : m_eval(eval), m_inner(0), m_outer(outerId), m_end(innerSize)
        {
        }

        EIGEN_STRONG_INLINE Scalar value() const { return (IsRowMajor) ? m_eval.coeff(m_outer, m_inner) : m_eval.coeff(m_inner, m_outer); }

        EIGEN_STRONG_INLINE inner_iterator_selector& operator++()
        {
            m_inner++;
            return *this;
        }

        EIGEN_STRONG_INLINE Index index() const { return m_inner; }
        inline Index row() const { return IsRowMajor ? m_outer : index(); }
        inline Index col() const { return IsRowMajor ? index() : m_outer; }

        EIGEN_STRONG_INLINE operator bool() const { return m_inner < m_end && m_inner >= 0; }

    protected:
        const EvaluatorType& m_eval;
        Index m_inner;
        const Index m_outer;
        const Index m_end;
    };

    // For iterator-based evaluator, inner-iterator is already implemented as
    // evaluator<>::InnerIterator
    template <typename XprType> class inner_iterator_selector<XprType, IteratorBased> : public evaluator<XprType>::InnerIterator
    {
    protected:
        typedef typename evaluator<XprType>::InnerIterator Base;
        typedef evaluator<XprType> EvaluatorType;

    public:
        EIGEN_STRONG_INLINE inner_iterator_selector(const EvaluatorType& eval, const Index& outerId, const Index& /*innerSize*/) : Base(eval, outerId) {}
    };

}  // end namespace internal

}  // end namespace Eigen

#endif  // EIGEN_COREITERATORS_H
